I can certainly understand your question. The Benelli M2 and the Winchester SX3 are both fine guns. I've owned Benelli shotguns since 1991 when I purchased my first SBE. They are all fine guns and the new M2 with the Crio barrel and the ComforTec recoil reducing stock, makes a very reliable gun, a much more comfortable gun.
I have been testing a Winchester SX3 since September of last year. I've used it for hunting doves, ducks, geese, fall turkeys, all clay sports and spring turkeys. I'm shooting the 3" gun with a 28" barrel. I chose to test the synthetic stock model, with the Perma-Cote gray finish on the barrel and receiver. It has the .742 back-bored barrel.
It's a great gun. It's very light and very quick. (I've seen Patrick Flannigan do things with this gun that are almost unbelievable.) It has not failed me in any situation thus far. I still need to shoot it in very hot and humid conditions here in Southern Illinois before my tests are through but I have little doubt that it will come through very well.
I've shot a variety of shotshells through it from light clay loads to 3" turkey loads, of all varieties. They all work well. It carries easily and balances in the hand naturally.
I'd recommend it and think you'd be very happy with it.
"If he's out of range, it just means that he has another day and so do you."